Early de-allocation of write buffer in an SSD

ABSTRACT

A data storage system includes: non-volatile solid state memory including non-volatile storage units and a temporary register; a data storage controller configured to receive a write command including a plurality of logical segments of data from a host; a write buffer allocated to receive a portion of the plurality of logical segments of data and accumulate a physical segment of data corresponding to a write unit of the solid state memory; a solid state memory controller configured to transmit the accumulated data from the write buffer to the temporary storage register each time the write buffer accumulates a physical segment of data. The data storage controller acknowledges completion of the write command to the host after the last logical segment of data is written to the write buffer; and deallocates the write buffer after the solid state memory completes reception of the accumulated data into the temporary storage register.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of U.S. Non-Provisional patent application Ser. No. 14/090,596, filed Nov. 26, 2013, entitled “EARLY DE-ALLOCATION OF WRITE BUFFER IN AN SSD,” which claims the benefit of U.S. provisional application No. 61/882,752, filed Sep. 26, 2013, each of which is hereby incorporated by reference in its entirety.

BACKGROUND

1. Technical Field

Apparatuses and methods consistent with the present inventive concept relate to data storage devices and more particularly to early de-allocation of a write buffer used to temporarily hold data before the data is sent to the data storage device.

2. Related Art

A data storage system may include various volatile and non-volatile storage devices such as a hard disk drive (HDD), an optical storage drive, and a solid state drive (SSD). In a SSD, a write buffer is used to temporarily hold data before it is sent to the memory controller to be written to the solid state memory, which may be, for example, but not limited to, a NAND device.

Generally, space in the write buffer is deallocated after the data in the write buffer is written successfully to the solid state memory. Referring to FIG. 1, data received by the SSD controller 110 is transferred by the controller front end 120 to the write buffer 130 where it is held before being sent to the memory controller 140. The memory controller 140 receives the data and transfers it to a temporary register 150 (e.g., page register that temporarily stores page(s) of data to be programmed) in the solid state memory 160 prior to the data being programmed into the nonvolatile memory units 170 of the solid state memory 160. After the data programming in the solid state memory 160 is completed successfully, the write buffer is de-allocated.

Programming the data from temporary register 150 to the solid state memory units 160 is a relatively time consuming operation (on the order of milliseconds) in comparison to other data transfer operations (on the order of microseconds) and causes significant delay in deallocating the write buffer. The delay in write buffer deallocation can result in reduced system throughput or require a large amount of buffer memory.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects and features of the present inventive concept will be more apparent by describing example embodiments with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram for illustrating a related art write buffer deallocation;

FIG. 2 is a block diagram for illustrating write buffer deallocation according to an example embodiment of the present inventive concept; and

FIG. 3 is a flow chart illustrating a method of write buffer deallocation according to an example embodiment of the present inventive concept.

DETAILED DESCRIPTION

While certain embodiments are described, these embodiments are presented by way of example only, and are not intended to limit the scope of protection. The methods and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions, and changes in the form of the example methods and systems described herein may be made without departing from the scope of protection.

Overview

Some embodiments of the present inventive concept provide systems and methods for early de-allocation of a write buffer.

FIG. 2 is a block diagram for illustrating write buffer deallocation according to an example embodiment of the present inventive concept. A solid state drive controller may receive commands and data from a host, for example, but not limited to, a server, a desktop client, or other device configured to transmit commands and data. Referring to FIG. 2, a SSD controller (data storage controller) 210 includes a controller front end 220, a write buffer 230, and a solid state memory controller 240. The solid state memory controller 240 interfaces with a solid state memory 260 and transfers data to and from the solid state memory 260. Although only one solid state memory is illustrated, one of ordinary skill in the art will appreciate that a plurality of solid state memory devices may be included without departing from the scope of the present inventive concept.

Data received from the solid state memory controller 240 by the solid state memory 260 is temporarily stored in a register 250, for example, but not limited to, a 16 KB (kilo-byte) page register, prior to being programmed into memory units 270 of the solid state memory 260. The solid state memory may include a plurality of temporary storage registers 250. The solid state memory 260 subsequently reads the data from the temporary storage register 250 and programs the data into non-volatile memory units 270 of the solid state memory 260.

Early De-Allocation of Write Buffer

Referring again to FIG. 2, the SSD controller (data storage controller) 210 may receive a write command from a host. The write command may include a plurality of logical segments of data. The controller front end 220 may allocate the write buffer 230 to receive at least a portion of the logical segments of data. The write buffer 230 may be configured as a plurality of buffers, where each of the plurality of buffers may be configured to accumulate a physical segment of data corresponding to a write unit of a nonvolatile solid state memory. A write unit is a smallest unit of data which can be written to a solid state memory, for example, a flash page in a solid state flash memory.

After the last logical segment of data from the plurality of logical segments of data included with the write command received by the SSD controller 210 have been transferred to the write buffer 230 by the controller front end 220, the SSD controller 210 transmits an acknowledgement signal to the host indicating that the write command has completed.

The write buffer 230 accumulates write units of data transferred by the controller front end 220 and after a write unit of data is accumulated in the write buffer 230, the write unit of data held in the write buffer 230 is transmitted to the solid state memory controller 240 which places the received data in a temporary register 250 in the solid state memory 260 prior to the data being programmed into the non-volatile memory units 270 of the solid state memory 260. The temporary register 250 in the solid state memory 260 may be configured as a plurality of registers. Multiple buffers within the write buffer 230 may accumulate write units of data prior to transferring the data to the temporary storage registers in the solid state memory 260.

According to an example embodiment of the present inventive concept, after the solid state memory controller 240 completes the data transfer to the temporary register 250 in the solid state memory 260, the solid state memory controller 240 transmits an acknowledgement signal to the controller front end 220. The controller front end 220 then deallocates the write buffer 230.

Thus, the write buffer 230 is deallocated after the data is stored in the temporary register 250 in the solid state memory 260 but before actual programming of the data to the nonvolatile memory units 270 is complete. Since the programming operation is relatively time consuming, de-allocating the buffer before completing the programming operation improves performance by reducing cycle time and enables the use of a smaller write buffer since buffer space becomes available sooner.

Upon completion of data programming into the nonvolatile memory units 270 by the solid state memory 260, the solid state memory 260 generates a programming status signal that indicates whether the data programming was successful. The programming status signal is transferred to the controller front end 220. While there can be a risk of data loss because the write buffer is de-allocated prior to the data being successfully programmed to the memory, the risk can be mitigated by the use of other nonvolatile memory, for example, but not limited to, magneto-resistive random access memory (MRAM), to store the data prior to transmitting it to the SSD controller, and/or using a Reed-Solomon coding scheme to enable data recovery.

In response to receiving a programming status signal indicating that data programming was unsuccessful, the SSD controller 210 may initiate data recovery procedures, for example, but not limited to re-reading the data from the memory unit indicated to be unsuccessfully programmed, reconstructing data using Reed-Solomon check pages, etc.

FIG. 3 is a flowchart illustrating an example embodiment of a method according to the present inventive concept.

Referring to FIG. 3, the SSD controller 210 receives a write command, which includes a plurality of logical segments of data, from the host (315) and a logical segment of data is sent to the write buffer 230 (320). The write buffer 230 acknowledges receipt of the logical segment of data to the SSD controller front end 220 (330). The process continues for all of the logical pages of data (335-Y). After the last logical segment of data has been sent to the write buffer 230 (335-N), the SSD controller 210 acknowledges completion of the write command to the host (340).

As data continues to accumulate in the buffers configured in the write buffer 230 (325), in a parallel operation when the write buffer 230 accumulates enough data to program a physical segment of data (i.e., a write unit) in the solid state memory 260 (350), the data is transferred to the solid state memory 260 by the solid state memory controller 240 (355) and stored in a temporary register 250 in the solid state memory 260 prior to the data being programming into the nonvolatile memory units 270 of the solid state memory 260 (360).

After each physical segment of data is placed into the temporary register 250 in the solid state memory 260, the solid state memory controller 240 sends an acknowledgement signal to the SSD controller front end 220, and the SSD controller 210 deallocates the write buffer 230 (365).

After the last write unit of data is programmed from the temporary register 250 into the nonvolatile memory units 270 of the solid state memory 260, the solid state memory 260 generates a programming status signal indicating whether the data programming was successful. The programming status signal is transferred to the controller front end 220.

In response to receiving a programming status signal indicating that data programming was unsuccessful (370-N), the SSD controller 210 may initiate data recovery procedures, for example, but not limited to re-reading the data from the memory unit indicated to be unsuccessfully programmed, reconstructing data using Reed-Solomon check pages, etc.

In example embodiments of the present inventive concept, multiple instances of operations 345-375 may execute with respect to multiple solid state memory devices within a solid state data storage system.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the protection. The methods and systems described herein may be embodied in a variety of other forms. Various omissions, substitutions, and/or changes in the form of the example methods and systems described herein may be made without departing from the spirit of the protection.

The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the protection. For example, the example systems and methods disclosed herein may be applied to hard disk drives, hybrid hard drives, and the like. In addition, other forms of storage, for example, but not limited to, DRAM or SRAM, battery backed-up volatile DRAM or SRAM devices, EPROM, EEPROM memory, etc., may additionally or alternatively be used. As another example, the various components illustrated in the figures may be implemented as software and/or firmware on a processor, ASIC/FPGA, or dedicated hardware. Also, the features and attributes of the specific example embodiments disclosed above may be combined in different ways to form additional embodiments, all of which fall within the scope of the present disclosure.

Although the present disclosure provides certain example embodiments and applications, other embodiments that are apparent to those of ordinary skill in the art, including embodiments which do not provide all of the features and advantages set forth herein, are also within the scope of this disclosure. Accordingly, the scope of the present disclosure is intended to be defined only by reference to the appended claims. 

What is claimed is:
 1. A solid state drive controller comprising: a controller front end configured to receive a write command including a plurality of logical segments of data; a buffer, coupled to the controller front end, configured to accumulate the plurality of logical segments of data; and a memory controller configured to initiate a transfer of the accumulated logical segments of data from the buffer to a temporary register in a nonvolatile solid state memory when the buffer accumulates enough data to program a predetermined number of physical segments of data in the nonvolatile solid state memory; wherein the memory controller is configured to initiate a deallocation of the buffer after the temporary register completes a reception of the accumulated data from the buffer.
 2. The solid state drive controller of claim 1, wherein the memory controller is configured to send an acknowledgment signal to the controller front end after the temporary register completes the reception of the accumulated data from the buffer.
 3. The solid state drive controller of claim 1, wherein the memory controller is configured to initiate the transfer of the accumulated logical segments of data when the buffer accumulates enough data to program one physical segment of data in the nonvolatile solid state memory.
 4. The solid state drive controller of claim 1, wherein the memory controller is configured to receive programming status information from the nonvolatile solid state memory indicative of whether the transferred data is successfully programmed at the nonvolatile solid state memory.
 5. The solid state drive controller of claim 4, wherein when the programming status information indicates that the programming of the transferred data is unsuccessful, the memory controller is configured to initiate the solid state drive controller to perform a data recovery operation.
 6. The solid state drive controller of claim 5, wherein the data recovery operation comprises reconstructing data using a Reed-Solomon coding scheme.
 7. The solid state drive controller of claim 1, wherein each physical segment of data comprises a smallest unit of data that can be written to the nonvolatile solid state memory.
 8. The solid state drive controller of claim 7, wherein each physical segment of data comprises a flash memory page.
 9. The solid state drive controller of claim 1, wherein the buffer is configured to accumulate the plurality of logical segments one at a time.
 10. A method comprising: receiving, at a controller front end of a solid state drive controller, a write command including a plurality of logical segments of data; accumulating, at a buffer coupled to the controller front end, the plurality of logical segments of data; initiating, by a memory controller coupled to the buffer, a transfer of the accumulated logical segments of data from the buffer to a temporary register in a nonvolatile solid state memory when the buffer accumulates enough data to program a predetermined number of physical segments of data in the nonvolatile solid state memory; and initiating, by the memory controller, a deallocation of the buffer after the temporary register completes a reception of the accumulated data from the buffer.
 11. The method of claim 10, further comprising sending, by the memory controller, an acknowledgment signal to the controller front end after the temporary register completes the reception of the accumulated data from the buffer.
 12. The method of claim 10, further comprising causing, by the memory controller, the transfer of the accumulated logical segments of data when the buffer accumulates enough data to program one physical segment of data in the nonvolatile solid state memory.
 13. The method of claim 10, further comprising receiving, by the memory controller, programming status information from the nonvolatile solid state memory indicative of whether the transferred data is successfully programmed at the nonvolatile solid state memory.
 14. The method of claim 13, wherein when the programming status information indicates that the programming of the transferred data is unsuccessful, the method further comprises causing the solid state drive controller to perform a data recovery operation.
 15. The method of claim 14, wherein the data recovery operation comprises reconstructing data using a Reed-Solomon coding scheme.
 16. The method of claim 10, wherein each physical segment of data comprises a smallest unit of data that can be written to the nonvolatile solid state memory.
 17. The method of claim 16, wherein each physical segment of data comprises a flash memory page.
 18. The method of claim 10, further comprising accumulating, at the buffer, the plurality of logical segments one at a time.
 19. A data storage system, comprising: non-volatile solid state memory comprising non-volatile storage units and a temporary register; a solid state drive controller comprising: a controller front end configured to receive a write command including a plurality of logical segments of data; a buffer, coupled to the controller front end, configured to accumulate the plurality of logical segments of data; and a memory controller configured to initiate a transfer of the accumulated logical segments of data from the buffer to a temporary register in the nonvolatile solid state memory when the buffer accumulates enough data to program a predetermined number of physical segments of data in the nonvolatile solid state memory; wherein the memory controller is configured to initiate a deallocation of the buffer after the temporary register completes a reception of the accumulated data from the buffer.
 20. The data storage system of claim 19, wherein the memory controller is configured to receive programming status information from the nonvolatile solid state memory indicative of whether the transferred data is successfully programmed at the nonvolatile solid state memory. 